Field of the Invention
This invention relates generally aircraft windows and, more particularly, to deformable aircraft cabin windows providing improved aerodynamics and lower drag.
Technical Considerations
Aircraft cabin windows are typically made of stretched acrylic. The cabin windows are installed in a frame attached to the aircraft fuselage. Conventional cabin windows typically have a semi-cylindrical cross-section in which the curved outer surface matches the outer curvature of the aircraft fuselage to provide a smooth outer surface of the aircraft. This reduces drag and promotes the overall aerodynamics of the aircraft.
At low altitudes, such as during takeoff and landing operations, there is little difference between the aircraft cabin pressure (interior pressure of the aircraft) and the pressure outside of the aircraft (exterior or atmospheric pressure). So, the cabin window retains its aerodynamic semi-cylindrical curvature matching the fuselage curvature. However, when the aircraft is at higher flight altitudes and the interior cabin pressure is relatively higher compared to the pressure outside of the aircraft, the cabin window can bulge or bow outwardly due to the pressure differential. This causes the outer surface of the cabin window to extend beyond the curvature of the aircraft fuselage, which creates an undesirable aerodynamic drag on the aircraft. This increased drag translates into increased fuel costs and lower cruising speeds.
This cabin window bulging can be reduced by using relatively heavy and rigid glass windows, which are stronger and less susceptible to bulging than thinner acrylic windows, or by increasing the thickness of the acrylic window to increase its strength and reduce the bulging. However, both of these solutions result in an increased weight penalty, which translates into lower fuel efficiency.
Therefore, it would be desirable to provide an aircraft cabin window which reduces or eliminates at least some of the problems associated with conventional aircraft cabin windows. For example, it would be desirable to provide an aircraft cabin window that retains the light weight of conventional stretched acrylic aircraft cabin windows but that reduces the aerodynamic problems associated with conventional aircraft cabin windows.